Alpha chain hemoglobins with electrophoretic mobility similar to that of hemoglobin S in a newborn screening program

ABSTRACT

OBJECTIVE: To characterize alpha-chain variant hemoglobins with electric mobility similar to that of hemoglobin S in a newborn screening program. METHODS: βS allele and alpha-thalassemia deletions were investigated in 14 children who had undefined hemoglobin at birth and an electrophoretic profile similar to that of hemoglobin S when they were six months old. Gene sequencing and restriction enzymes (DdeI, BsaJI, NlaIV, Bsu36I and TaqI) were used to identify hemoglobins. Clinical and hematological data were obtained from children who attended scheduled medical visits. RESULTS: The following alpha chain variants were found seven children with hemoglobin Hasharon [alpha2 47(CE5) Asp>His, HbA2c.142G>C], all associated with alpha-thalassemia, five with hemoglobin Ottawa [alpha1 15(A13) Gly>Arg, HBA1c.46G>C], one with hemoglobin St Luke's [alpha1 95(G2) Pro>Arg, HBA1c.287C>G] and another one with hemoglobin Etobicoke [alpha212 84(F5) Ser>Arg, HBA212c.255C>G]. Two associations with hemoglobin S were found one with hemoglobin Ottawa and one with hemoglobin St Luke's. The mutation underlying hemoglobin Etobicoke was located in a hybrid α212 allele in one child. There was no evidence of clinically relevant hemoglobins detected in this study. CONCLUSION: Apparently these are the first cases of hemoglobin Ottawa, St Luke's, Etobicoke and the α212 gene described in Brazil. The hemoglobins detected in this study may lead to false diagnosis of sickle cell trait or sickle cell disease when only isoelectric focusing is used in neonatal screening. Additional tests are necessary for the correct identification of hemoglobin variants.